Tachycardial rhythm problems of the heart include atrial fibrillation. Neurological stimulus-conduction problems in the heart may stimulate the atrium at high frequency. In other tachycardia, such as ventricular tachycardias (VTs), complete contraction does not occur, causing defective pumping output of the heart. Classically, the occurrence of tachycardia is reduced by taking medications continuously, or is eliminated by a heart operation in which the stimulus-conduction tissue is severed in certain parts of the heart.
VTs originate in so-called “reentrant circuits”, which may typically created in, or in the boundary of, electrically non-active myocardial scar tissue, but may have other causes as well. Recently, a minimally invasive therapy method has become established, where an ablation catheter is introduced via a vein and “burns” the interfering stimulus-conduction paths, for instance with high frequency (RF) electrical energy.
Until now, minimally invasive diagnosis and treatment of tachycardial rhythm problems have been performed with an angiographic X-ray system (see, for example, DE 4436828, “Röntgendiagnostikeinrichtung mit einer Steuervorrichtung für zwei C-Bögen” [“X-Ray Diagnosis System with a Control Device for Two C-Arms”]), a device for recording the intracardial EKG, and a device for “burning out”, or ablation, of the stimulus-conduction problem regions (see, for example, U.S. Pat. No. 5,365,926, “Catheter for Mapping and Ablation and Method Therefore”,) which may be available as a product as the Carto-Mapping system from Biosense Webster. In electrophysiology, this treatment method is generally known as high-frequency ablation or RF ablation. The method for measuring the electrophysiological potentials in the heart for determining the correct ablation site in each case is called mapping.
U.S. patent application Ser. No. 11/486,356, “Method and Apparatus for Treating Tachycardial Rhythm Problems”, teaches a way of treating rhythm problems where a display of 3D images of the heart and of the required therapy tools is possible in real time.
U.S. patent application Ser. No. 11/653,489, filed on Jan. 16, 2007, entitled “Device and Procedures for Cardiac Treatment with a MRI X-Ray Hybrid System” teaches a way of treating rhythm problems using a magnetic resonance imaging modality (MRI) and a C-arm X-ray device, and where the MRI image and the CT-like image obtained by processing the X-ray data are fused. The MRI image is used to identify scar tissue in the patient heart, so as to register the scar tissue regions with respect to the CT-like imaging data.
A so-called DynaCT (Siemens AG, Munich, Germany); permits computed-tomography-like (CT-like) soft-tissue examinations of biological tissue. By recording images that are synchronized with an electrocardiogram (EKG) signal, and by subsequent image reconstruction and image selection, it is possible to obtain 3D soft-tissue images of the beating heart.
In performing electrophysiological ablation procedures in the right or left ventricle, one or more catheters are introduced into anatomical areas of the heart to perform electrophysiological mapping and/or ablation. When performing ablation therapy inside the left or right ventricle, for treating ventricular tachycardia (VT), for example, conduction lines or foci that trip the tachycardia may obliterated by, for example, RF ablation. By repeated stimulation of various points of the endocardium, the attempt is made to initiate the tachycardia, and then to treat the syndrome permanently in a targeted way by obliterating tissue at the stimulation site.
VT procedures may presently take more than 5 hours, which may result in a high radiation dose to the patient, yet have an inadequately high success rate, and have the risk of damage to the cardiac muscle function from overly aggressive ablation.
Papillary muscle areas of the heart are not directly visible in currently available radiological scans or electro-anatomical maps. When VT ablation procedures in which myocardial areas in the vicinity of the papillary muscles are to be obliterated, it is difficult to guide the catheter unambiguously to the endocardium, particularly since the myocardium and the papillary muscles move with the heartbeat.
Damage to the papillary muscles should be avoided or minimized. The more aggressively the ablation procedure is performed, the less is the likelihood that the arrhythmia will recur. But, with an aggressive ablation procedure, the risk of adverse effects on the ventricular function or of damage to surrounding structures, including the papillary muscle areas, increases.